Core Sound 20 Hull #102

[Charlie Jones]

;D

It's just that I'm a plane freak ;D

I love 'em and it just grates my soul to hear one hit something hard. You are probably right as to the effectiveness- it's just that to me, as an long time woodworker, it's somewhat like using a chisel to open a paint can

But still, try one of the Surforms. It's amazing how quickly those will cut down epoxy, particularly when it's still a bit green.Amazon lists one for 5.05 right now by the way-

http://www.amazon.com/Stanley-21-399-6-Inch-Surform-Pocket/dp/B00002X1ZQ

And if you want a totally unbelievable tool for cutting down epoxy, take a shot at the Shinto Rasp sold through CLC, Also works on wood.

http://www.clcboats.com/shop/products/supplies/tools/SHIN-SR000.html

Most of my planes are older ones that I've collected over the years. Here's a part of my planes. Not shown here are the conversion planes with iron tops and wooden soles, nor the old wooden ones.

Oh- and for the purpose of the picture is the ONLY time those planes get set down on their soles. Otherwise they are laid on the side so the iron doesn't touch.

[JeffM]

nifty thing about the Sureform (besides my not minding abusing it) is that it has so many "blades"--one pass equals a good many with a plane.  Picture a file or rasp, but with blades in place of ridges.  I'm going to look on Amazon--my local box store stopped carrying the one that handles like a plane.

[wkisting]

Yes, the sureform is handy for knocking down epoxy quickly, but you've got to be careful or you can gouge or tear out the wood terribly. I'm sure experienced woodworkers can handle it fine, but newbies like myself (I've only used mine a handful of times) seem hard-wired to start applying more pressure and effort to the tool than it actually needs. So everything is going along very effectively and then SCREEEEEEECH, it gouges into a surface because you got sloppy with how you were holding it... Of course, a block plane can do that too, but it's a little safer since the depth is controllable. It does dull the blade quickly, but like Ray, I find it very handy for clean up, now that I know how to sharpen it back to a razor edge.

Flipped the boat yesterday. Sanded and filled a lot of the hull today. All the seams between panels are nice and smooth now, but tomorrow I'll sand and fill (very thinly) again as the epoxy tends to shrink a bit and I've found that the flat seams come out flatter if you sand-and-fill them twice. (Got more screw holes to fill anyway).

I'm VERY impressed with how fair the hull is to begin with. It's a real credit to the quality of Graham's lines (and to the care with which we cut and folded the panels to begin with). There will be very little filler needed to fair the hull, and most of it is simply to ensure a smooth transition at the scarf joints (which chipped at the thin edges a bit, as they often do). Very cool.

Here's some pics... In the first pic, that's me in orange at the stern, next to two of my colleagues, and two of my students at the bow. There's two more students and one more colleague on the other side of the boat, and then my wife and two others standing around snapping pictures. We had way more people on hand than needed... the boat is impressively light... I'd estimate only about 400 lbs. at this point, which is lighter than I expected with so much of the structure in place. The flip went very easily... we rolled it over on the transom in less than a minute.

[JeffM]

Wes, looks very good!  I'm curious how you're going to do the forward seat.

[wkisting]

Jeff, the tops of the stringers that support the forward seat are still unsealed (to take glue later). I left the forward seat off so that I can paint the space beneath it first. Then I'll glue in the forward seat, add a layer of 'glass and carefully blend the edges of the 'glass into the finished side seats. I just thought it would be easier than trying to crawl around and paint the underside later. [Edit to add: Also, it's difficult to see in the picture, but I attached stringers to the outside faces of the finished seats to provide a "landing" for the edges of the forward seat... just realized that might be what you're wondering about. I blew up the picture to make them a little more visible (see below)]

Ray, that cheese-grating effect is what I've experienced with the sureform also. I assumed it was inexperience on my part, so it's nice to hear that some of you pros have the same trouble.    I get the sense from Charlie's post, however, that he's figured out how to manage the tool so that it doesn't damage the wood. I suspect it's possible, but I can't knock off all the epoxy without doing at least a little damage to the wood grain (using the sureform), which is why I favor the block plane as you do. But there's no question the sureform is quicker if the epoxy is thick or very irregularly spread.

[wkisting]

For those who have attached stainless flat bar or half-round along the keel line of a CS... what do you screw into for the first 6 feet?

I realize you can screw into the exterior keel (or interior keel batten) from the forward bulkhead to the transom, but how does one attach the stainless to the forward portion of the keel (from the deck, down the front of the bow, wrapping under before it sweeps aft), where there is only the 1/4" plywood and the fillet at the centerline? Do I need to add a solid wood backer?

[Garry]

An idea: Drill the holes oversize and fill with thickened epoxy. Then drill the holes undersize and use sheet metal screws to self-tap the holes. The epoxy can take a thread readily, especially sheet metal screw thread. Also, check Gougeon's book, they have a detail about forming threads in epoxy.

Another idea that Ray Henry used is to set a thread insert into the epoxy but I had some failures when I tried it this way.

[wkisting]

Thanks Garry... that sounds like a good solution. I suppose as long as the sheet metal screws have at least 1/4" bite into the epoxy, that would be adequate to hold on the stainless. Should bend fairly readily to the hull if I "pre-bend" it a bit. I found 6' long sections of 3/4" quarter-round stainless at McMaster-Carr for $40... its 304 stainless (the common variety, less corrosion resistant), but since we have no plans to store our boat in saltwater (and most use will be freshwater at the LARGE lake near us), that should be fine. Just have to rinse it good after any trips to the ocean. And if I use sheet metal screws as you suggest, should be easy to replace if need be. I'll probably use the quarter-round for the first 6 feet (enough to wrap down and under the bow), then switch to cheaper 1/8" thick x 3/4" wide flat stainless bar for the rest of the way.

Got the bottom sheathed today... that was a big job. Took Anna and I a little over 5 hours to complete it.    Still have to do the fill coats (one tonight, one or two more tomorrow), but those will go MUCH quicker. We used 6 oz. glass and overlapped it at the seams so there's at least two layers of 6 oz. covering each exterior seam. We added some 6 oz. tape to the first 6 feet of the keel line and a little bit of reinforcement along the first foot of the bow/hull as well... mainly for some added abrasion resistance when beaching the bow on the sand. we were going to add an extra reinforcement patch covering the whole 1/4" thick portion of the forward hull, but decided it's probably not needed. We'll baby our boat anyway, as we always do.

[paul_stewart]

Wes, 

See this previous post on the B&B forum...

http://www.messing-about.com/forums/index.php?topic=5825.msg50077#msg50077

...regarding the solution that Alan and I used on CS20 #103, "Dawn Patrol": 

We used locknuts embedded at the bottom of oversized epoxy-filled holes along the keel.   That post discusses the testing we performed.

I would add that we found that relying on "threaded epoxy" alone to hold the screw was not successful.  In contrast, embedding locknuts was successful.  The general idea is that the nut is started part-way up the screw and then the nut+screw and epoxy are placed in the hole.  After 10 hours the screw is removable but the nut will stay in place.   I would recommend these steps:  wet out the hole with epoxy so that there is a 1/16"deep pool of epoxy in the bottom of the hole; after a few hours half fill the hole with epoxy and squish in the screw+nut;  the epoxy should be near level with the top of the hole;  as it cures the epoxy may shrink/settle down so that a little more epoxy is needed to fill the hole to the top.  When tightened, you do not want the bottom end of the screw to penetrate through the epoxy into raw wood; rather, you want the entire screw+nut assembly to be encapsulated in epoxy.

Do your own tests on some scrap wood.  We used slightly thickened epoxy for our keel guard holes,  but some of our later work on the "Dawn Patrol" indicated to us that unthickened epoxy may be stronger than thicked epoxy.   

Because of minimal thickness of the bow section,  we used shorter screws with plain nuts (not lock nuts) in the bow.  We used longer screws with locknuts midship and aft along the keel.

Below you can see a photo of some early testing we did in scrap lumber.  (For this illustration the wood was carefully cut away with a saw and a sander.)  When Alan over tightened the screw with a washer in place,  the washer deeply crushed into the top of the wood and the nut+epoxy never moved.

[wkisting]

Thanks Paul... I knew I had seen a post about this, but forgot where...  Embedding the nuts is a great idea. I'm not worried about it along the keel, but I suppose I'll have to be careful along the bow because I don't think I've got much depth at all to work with.

[wkisting]

On attaching the keel... I'm sure I'll want to use screws to keep the keel aligned while the epoxy sets. Is it best to leave screws in and bury them in epoxy, or should I remove them?

I know the screws would give some extra strength, but on the other hand, if the keel ever rots and needs to be cut off flush (which may never happen), I'm sure I'll wish I removed the screws. Just curious what others do/think about this.

[Roger Peterson]

Hi Wes,

I used bronze screws to attach the keel on my CS-17. I wanted the security of the mechanical fasteners but if the time came to replace or service the keel wood, the bronze screws can be cut off without damage to the saw or plane blades. I also put 2 layers of glass tape on each side of the keel but not over the "top". All can be easily cut and ground flush for repair or replacement.

Roger

[Garry]

I figure the epoxy bond and a small fillet on each side is plenty strong. If you hit something hard, the wood will absorb the damage before the bond and fillet would break. I used temporary fasteners, then removed them and filled the holes. That way, I don't have to worry about leakage around a fastener getting to the wood and starting rot.

[Dale Niemann]

Wes,

"Lively" has stainless steel piano hinges mounted on top and they have been very satisfactory.  I think fiberglassing the hatches is a little overkill.  I walk on mine all the time and have had no problems.  Of course I only weigh only 160 lbs.

Dale

[tom151]

On attaching the keel... I'm sure I'll want to use screws to keep the keel aligned while the epoxy sets. Is it best to leave screws in and bury them in epoxy, or should I remove them?

I know the screws would give some extra strength, but on the other hand, if the keel ever rots and needs to be cut off flush (which may never happen), I'm sure I'll wish I removed the screws. Just curious what others do/think about this.

Just another opinion as I haven't seen the detailed plans for the CS20...

I've never liked leaving any metal fasteners in a wood-epoxy boat. Many repair jobs I had to do come from metal fasteners embedded in boats that were supposedly 'safe' because they were encapsulated. As for adding strength - not any measurable amount in my opinion.

Yes, sometimes it's necessary to use sheet-rock screws to hold pieces in position till epoxy goes off - but I would remove them then fill all holes using extended epoxy. I use an epoxy hypodermic stuck all the way to the bottom of the hole - making for solid (no air bubbles) fills, fast and easy.

As for a 'rubbing strip' along the centerline to protect the bottom of the boat... I would consider it to be sacrificial and use a strip of wood and leave it plain (not glassed).  - I'd build base of heavy glass/kevlar/carbon reinforcements along the join of the bottom plywood before adding any keel stock - then add the sacrificial wood strip glued directly to that - no glass over, no fillet either - You don't want it to be strongly attached after all, it's supposed to be sacrificial, to take the damage and NOT cause damage to the underlying bottom ply or covering.

The approach I like best is to build the wood strip out of several pieces using a very steep scarf (almost a butt join) so that when it gets damaged, and you know it will, any splitting along the grain gets terminated at the butt joins - makes it easier to remove a section and easily patch in a replacement. The epoxy joins also act as a barrier to water/rot migration.

I did see pix somewhere of a SS strip held on with screws... personally I would be concerned that shock impacts to the SS strip in the area of the screws would tend to break the seal between the SS and the epoxy encapsulating it - opening a path for water migration.

My 2 cents,

[wkisting]

Well, cut the CB slot in the hull (used router with a flush trim bit--worked great), 'glassed over the edges with one layer of 6 oz. tape (rounded the edges around the slot with 1/4" roundover bit on the router first), then glued-and-screwed on the keel, then filleted and 'glassed both sides of the keel. I've decided to remove the fasteners and fill the holes, so I'll just inject epoxy with a syringe tomorrow and that should take care of it.

I think the stainless rub strip is a good idea, so I ordered from McMaster-Carr. One 6' section of 3/4" half-round, along with three more 6' sections of 1/8" thick (3/4" wide) flat bar. All 304 stainless... total cost after shipping was $119, which is pretty good. My dad (steel fabricator) could've gotten it for me cheaper (or free), but it would've taken awhile to get it to me. McMaster-Carr shipped it and had it at my door step in less than 24 hours, which I couldn't believe. (I didn't select overnight shipping, nor did I get charged for it.) I'll try the trick of epoxying in the nuts so I can install the stainless rub strip with machine screws. I extended my keel an extra 1.5' forward to give me some extra thickness for burying the nuts in the forward portion of the hull, as well as a smoother, more gradual transition from keel-to-hull at the bow. I've noticed there's an abrupt transition on many of the other hulls I've seen in pictures, but I want the stainless to be able to "step up" onto the keel without a crimp or bend.

Ray, about bottom paint... I ended up chickening out and going back to my original idea of VC Performance epoxy paint. I really doubt I'll ever keep our CS20 in saltwater for longer than a week (maybe two), so I don't technically "need" an ablative paint. I've heard the teflon in the VC Performance does an adequate job keeping marine growth from attaching. I'm more interested in its (apparently) superb durability to hold up to riding on a trailer. Also, several local fellows (including one at West Marine) told me I would absolutely regret putting bottom paint on a trailerable boat after about 4-6 years (including those hybrid and ablative kinds formulated for trailer use). They said it always works well at first, but that they've seen a lot of trailer boats begin to acquire blistered or swiss-cheese finishes as additional layers of bottom paint are applied. I don't know if that's true, but after hearing it from 3 different people (2 of whom claim it happened to them... the third was the West Marine guy, who said he's "seen it happen" on others' boats), I decided just to go with a hard, durable epoxy paint (VC Performance has no ablative properties, unlike VC Offshore or VC-17). The downside, of course, is that if I don't like it, I may not be able to paint over the VC in the future with anything other than another teflon-impregnated epoxy paint, but I suspect I'm going to like the stuff anyhow, so hopefully that won't be an issue.

Dale, after hearing from you and Ray, I'll probably just use top-mounted piano hinges also. I thought it would look funny, but it will be much easier to install and maintenance than if I try to hide them in the seam on the back edge of the hatch. Ray suggested rounding the corners a bit, which I'll certainly do to make them look a little more "finished." West Marine's piano hinges (stainless) are pricey. Anyone know of a cheaper supplier that I can order these from? (I'll need four hinges, each 2' long... or I could cut down a longer length also.)

[Edit to fix a misplaced modifier... hey, I'm an English prof., what do you expect?    ]

[wkisting]

Yeah, they tell me the more common problem is with so-called "modified epoxy" bottom paints (I think I got that term right... not sure) that are designed for trailerable boats, but are meant to be either ablative or biocide-impregnated. Apparently, the epoxy creates hard spots, but voids are created in places where the epoxy either isn't distributed well or where the ablating ingredients "clump"... The West Marine guy said it usually takes a few re-paints before it occurs... after the thickness builds up a bit. He even warned me against buying West Marine's brand of bottom paint for a trailerable boat. (I was going to buy a basic multi-season ablative as you suggested.)

Again, it's possible these folks are exaggerating or confusing the kinds of paints (I've received patently incorrect advice from West Marine before), but I'm sure this is what they told me, so I decided to "play it safe" by avoiding those kinds of bottom paints all together. I've heard several rave reports about the VC Performance, and it seems like the right paint for our use (trailer-stored, almost exclusively day-sailing, with perhaps a 1- or 2-week trip only once per year). If I were likely to store our boat in the water with any kind of regularity or for extended periods, I would certainly take the risk on the multi-season ablative as you recommended.

I would be curious to know if anyone reading this post has had trouble with ablative or biocide paints on trailered boats... I also wonder if the folks who told me they had trouble maybe prepped or applied their paints incorrectly, which very likely could explain the swiss-cheese finish (a partially-crusted bottom with hard spots and scattered "pores" or "voids") that they described to me.

[Garry]

Wes,

For good advice regarding trailering small boats, I recommend you post a question at the Trailer Sailor bulletin board - a great bunch of folks.

http://bbs.trailersailor.com/forums/tsbbcomp/trailersailor/index.cgi

[wkisting]

Thanks Garry, I do pop over there on occasion to read around, but I've never posted.

Thought some of you might like to see our keel. We made it longer than the plans show so that we could blend it imperceptibly into the bow curve. Used an 18' long piece of 5/4 x 3 Douglas Fir. Rough cut it, glued it in place, then removed the fasteners and planed it down carefully until the bow curve rolled smoothly into the keel. This way, our stainless rub strip won't have to "step up" onto the keel. We're really pleased with how it turned out, as it seems we'll be able to bend the 3/4" half-round to the curve by hand, with little pressure and no need to pre-roll the steel.

[wkisting]

Okay, I found an awesome way to apply epoxy fill coats quickly, evenly, cheaply, and in a manner that is virtually idiot-proof. After hearing Charlie's criticism of foam brushes and trying his idea of cutting up a paint roller to "make" brushes (which, by the way, does work better since the roller brushes hold up better than the foam disposable kind and apply just as smoothly), I decided to try another kind of foam roller that is sold at Home Depot. In the past, I had horrible results when I experimented with their cheap yellow foam rollers, but they sell an "ultra-fine" foam roller for more money ($7 per pack of 5) that is absolutely TERRIFIC for fill coating.

I just applied an extraordinarily smooth, even fill coat to my entire CS20 in under 15 minutes, without wasting a single drop of epoxy even on the vertical or near-vertical surfaces (transom and hull sides). Here's the secret:

Heat the epoxy resin and hardener to thin them out (before mixing them together, of course... I used a small space heater and sunlight), then mix a small batch of epoxy and pour it into a small, shallow aluminum pie tin (the rectangular kind, about 6" x 8"). Then wet the roller THOROUGHLY in the epoxy in the aluminum tin tray. The roller has to be fully saturated the first time or it will roll tiny air bubbles into the epoxy. Then go ahead and roll epoxy onto the boat. [Edit to add: I'm using Raka 127 resin and their SLOW 606 hardener. Those of you using fast hardener may find that heating the resin increases cure speed too much, so this *may* be a good option only for folks using slow hardeners, which I find perfect for the GA weather.]

It is amazingly simple and startlingly quick... easier than any of the dozen other tricks/tools I've tried in the course of the three boats I've built. And it makes vertical surfaces a breeze because if you start rolling slowly for the first 2-3 revolutions of the roller, absolutely NO epoxy gets "slinged" off the roller or dripped onto the ground. I worked quickly, rolling fore and aft in 3' long strokes to apply the coat. After coating the entire boat, I went back (without dipping into more epoxy) and ran the roller athwartships (perpendicular to the keel) with overlapping strokes as I worked from bow to stern. This second pass knocks out any irregularities that didn't get smoothed during the first pass (which are very few) and prevents sags if you're working in a high-humidity climate like me. It also leaves a finish so fine and smooth that it looks like no thickness has been added. Of course, if you stick your finger in the wet epoxy (which I was fooled into doing several times) you quickly realize that there is a nice, even coat of epoxy sitting nice and flat on top of the previous surface.

I can't tell you how much easier this is than using foam brushes. And I also find it easier (quicker, in particular) than the cut-up foam roller trick that Charlie described on another post. Here's a pic of the rollers I used... I noticed that there are several different brands of "ultra-fine" foam rollers, but this pack appeared of noticeably better quality than the other kinds, so I can't vouch for all such rollers.

[Edit to add: By the way, I did the entire boat--two passes to apply one fill coat--with just one of these rollers. They do tear off, but not for a LONG time, and when they begin to deteriorate, they break off so slowly and predictably that you rarely get any bit in your coat. In my case, only the end of the roller tore off, and it tore off in a perfect circle that was easy to remove and then keep going.]